Rates of Change in Soil Structural Stability under Forages and Corn

Abstract

Data on rates of change in soil structural stability under different cropping systems are scarce. Field measurements of changes in dispersible clay (DC) and wet aggregate stability (WAS) were made during 3 yr in six forage treatments and conventional and zero‐till corn (Zea mays L.). The study was conducted on a silt loam soil (fine‐silty, mixed, mesic Typic Haplaquept intergrading to fine‐silty, mixed, mesic Typic Eutrochrept) near Elora, ON, Canada. The DC and WAS changed exponentially with soil water content at time of sampling and were adjusted for this parameter before calculating changes with time. No increases in structural stability occurred during the 3‐yr time period within the corn treatments. In contrast, all of the forage treatments resulted in highly significant rates of structural improvement. A half‐life parameter was used to quantify these changes. Calculated half lives for the different forages were similar in magnitude, being approximately 2.7 and 5.4 yr for DC and WAS, respectively. Across the treatments, highly significant correlations were found between rates of structural stabilization and mean root length (r = −0.57 for WAS, significant at P = 0.01), mean root weight (r = −0.56 for DC and −0.65 for WAS, significant at P = 0.01) and the coefficient of variation for soil water content (r = −0.64 for DC and −0.56 for WAS, significant at P = 0.01). Forages may promote structural improvement through their influence on the amplitude of wetting and drying cycles. In addition, large increases in stability were observed over the intervening winter months, suggesting a freeze‐thaw effect.

Freezing Effects on Aggregate Stability Affected by Texture, Mineralogy, and Organic Matter

“…This increase was statistically significant at water contents of 0.10 and 0.20 kg kg-' for the Palouse silt loam, one of the soils highest in organic matter (Table 1). Increases in soil aggregate stability with increasing freeze-thaw cycles have also been detected by others (H. Kok, 1989, personal communication; Mostaghimi et al, 1988;Perfect et al, 1990). For the Barnes loam and Portneuf silt loam at a 0.30 kg kg-' water content, the increase in stability with one freeze-thaw cycle was minimal, averaging less than three percentage points.…”

Erosion and Sedimentation Processes on Irrigated Fields

“…Particle-to-particle bond formation, stabilization, and disruption processes are poorly understood. Recent investigations have focused on soil bonding constituents (Kemper and Koch 1966;Lehrsch et al 1991;Uehara and Jones 1974), the bond formation process (Blake and Gilman 1970;Utomo and Dexter 1981;Kemper and Rosenau 1984;Kemper and Rosenau 1986), bond persistence and change (Kay 1990;Lehrsch and Jolley 1992), and bond disruptive forces such as wetting (Panabokke and Quirk 1957;Koch 1966, Arulanandum et al 1975;Kemper et al 1975;Kemper et al 1985b) and freezing (Bullock et al 1988;Lehrsch et al 1991;Mostaghimi et al 1988;Perfect et al 1990). Mechanical measures of soil strength such as vane shear tests and fall cone penetrometer tests (Franti et al 1985) have been used to attempt to quantify soil resistance to hydraulic detachment.…”

Atributos físicos de um argissolo e rendimento de culturas de acordo com o revolvimento do solo em plantio direto

“…Os sistemas de manejo influenciam diretamente as propriedades estruturais do solo, uma vez que a agregação depende, dentre outras coisas, do conteúdo e tipo de matéria orgânica, sistemas de culturas (Perfect et al, 1990), atividade biológica (Lehrsch & Jolley, 1992), preparo do solo e tráfego de máquinas (Kay, 1990) e, ainda, de variações de umidade e temperatura no solo. Deve-se salientar que a instalação do experimento em estudo foi em solo com pastagem natural, com boa estrutura, ao contrário da maioria das lavouras em plantio direto que tem partido de uma estrutura degradada de solo.…”